Preheat oven to 350 degrees.
Grease cake pans.
In mixing bowl, cream butter and granulated sugar until smooth and creamy.
Beat in one egg at a time. Be sure to beat each egg well.
In second mixing bowl, combine your dry ingredients.
Gradually mix in dry ingredients and sour cream. Alternate between each until all is well incorporated.
Add vanilla to batter and fold in your mashed bananas.
Pour evenly into your greased cake pans.
Bake in preheated oven for 25-30 minutes. Your cake is done when inserted skewer comes out clean.
Remove cake and cool on wire rack.
When cake is completely cool, frost and serve.